Plasma-arc spraying torch

Abstract

A plasma-arc spraying torch is disclosed which comprises a cathode unit and a separable anode unit which units are connected to each other approximately at a section of the torch in which the cathode of the torch is mounted on a cathode supporting member. The connection of the units and the mounting of their parts are all self-centering. Each unit has its own separate cooling circuit. Cooling of the anode nozzle is provided by a helical water duct within a nozzle holder member surrounding the anode nozzle. The nozzle holder and cathode supporting members are each at least laterally embedded in body parts of insulating material.

I claim: 
     
       1. A torch for plasma-arc spraying of powdered materials, comprising a cathode unit and a separate anode unit connected to each other, each of said units being provided with a separate cooling circuit having each a water inlet and a water outlet connection, the cathode unit comprising an outer body part of insulating material, a cathode supporting member embedded in said body part and provided with the cathode cooling circuit, and a cathode part mounted replaceably on the said cathode supporting member, the anode unit comprising an elongated nozzle part forming the anode and a nozzle holder member laterally surrounding the said nozzle part, the nozzle holder member comprising at least two coaxial parts and being provided with an anode cooling circuit adapted to assure a forced cooling water flow along the nozzle part, the anode and cathode units each further comprising means for automatic centering these units in their connected state, and wherein the connection surface of the anode and cathode units is situated substantially in a section of the torch in which the cathode part is mounted on the cathode supporting member, said separate cooling circuits for said cathode and anode units being respectively self-contained within said units, whereby said units can be disassembled from one another for replacing one or more of said cathode part and said nozzle part without disturbing the continuity of said respective separate cooling circuits. 
     
     
       2. A plasma torch in accordance with claim 1, wherein the cathode part and the cathode supporting member have at least one plane contact surface. 
     
     
       3. A plasma torch in accordance with claim 2, wherein the cathode part is mounted on the cathode supporting member by means of a cap screw. 
     
     
       4. A plasma torch in accordance with claim 3, wherein the cap screw and the cathode part have respective conical adjusting surfaces for automatically centering the cathode part on the cathode supporting member. 
     
     
       5. A plasma torch in accordance with claim 1, wherein the cathode part is constituted by an outer electrode part of tungsten and a core part of copper. 
     
     
       6. A plasma torch in accordance with claim 1, wherein the nozzle part has a conical lateral outer surface and the nozzle holder member has a corresponding conical inner surface, a coaxial fixing sleeve being fitted in the nozzle holder member adjacent the broader end portion of the nozzle part. 
     
     
       7. A plasma torch in accordance with claim 1, wherein the nozzle holder member comprises a lateral mantle part of insulating material. 
     
     
       8. A plasma torch in accordance with claim 1, wherein the nozzle holder member comprises a water duct surrounding the nozzle part, the inlet of the duct being placed at the downstream end of the nozzle part. 
     
     
       9. A plasma torch in accordance with claim 8, wherein the cooling water duct is helically arranged around the nozzle part. 
     
     
       10. A plasma torch in accordance with claim 1, wherein the nozzle holder member comprises first and second coaxial parts fitted inside one another and defining a cooling water duct there between, and wherein the surface of contact between the said two parts of the nozzle holder member is a conical surface. 
     
     
       11. A plasma torch in accordance with claim 1, wherein the nozzle holder member has a protruding holding part having holding slots for holding powder injection pipes, a holding member mounted to said protruding holding part for maintaining the powder injection pipes in said slots, the said holding part being formed around the downstream end of the nozzle part and containing a cooling water duct. 
     
     
       12. A plasma torch in accordance with claim 11, wherein the inlet of the water duct of the protruding holding part is connected with the inlet connection of the anode cooling circuit, the outlet of the said water duct of the holding part being connected to a cooling water duct surrounding the nozzle part.